This project will continue the close monitoring of side effects and adherence of subjects enrolled during 1985-1987 in the Seattle- based phase II and phase IV studies "Chemoprevention of Lung Cancer with Retinoids/Beta-carotene in Smokers" and "Cancer Prevention with Retinol and Beta-carotene in Persons Occupationally Exposed to Asbestos". Two high-risk populations have been randomized to placebo or retinol/beta-carotene to evaluate recruitment, adherence and possible side effects of these agents in preparation for a full-scale trial to assess chemopreventive efficacy. Follow-up will consist of phone or clinic contacts every 3 months, plus subject-initiated calls or visits as indicated to assess symptoms or physical findings consistent with beta-carotene/retinol side effects. Laboratory studies will be repeated yearly. Because side effects and adherence are related to the duration of treatment, we propose to closely monitor the 1700 subjects enrolled in these two studies for an additional 5 years. Defining long-term side effects and their relationship to adherence, serum concentrations of relevant analytes, cumulative dose, and other variables is crucial to the development and implementation of any large-scale population studies using retinol and/or beta-carotene. The subjects enrolled in this trial will serve as a Vanguard Group for our full scale efficacy trial allowing for a more streamlined, cost-effective side effect monitoring system in that trial.